Surface emitting semiconductor laser and its manufacturing method, surface emitting semiconductor laser device, optical transmitter, and information processor

ABSTRACT

A surface emitting semiconductor laser includes a substrate; a first semiconductor distributed bragg reflector of a first conductive type; an active region; a second semiconductor distributed bragg reflector of a second conductive type; a current confinement layer that confines current in the active region; an optical confinement layer that confines light in the active region; and an optical loss unit including center and periphery portions in a predetermined direction, and gives a larger optical loss to the periphery portion than that of the center portion. Also, Do 1 &lt;Do 2  and Dn&lt;Do 2  are satisfied, where Do 1  is a width of an optical confinement region of the optical confinement layer in the predetermined direction, Do 2  is a width of a current confinement region of the current confinement layer in the predetermined direction, and Dn is a width of the center portion of the optical loss unit in the predetermined direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 fromJapanese Patent Application No. 2012-011724 filed Jan. 24, 2012.

BACKGROUND

The present invention relates to a surface emitting semiconductor laserand its manufacturing method, a surface emitting semiconductor laserdevice, an optical transmitter, and an information processor.

SUMMARY

According to an aspect of the invention, there is provided a surfaceemitting semiconductor laser including a substrate; a firstsemiconductor distributed bragg reflector of a first conductive typeformed on the substrate; an active region formed on the firstsemiconductor distributed bragg reflector; a second semiconductordistributed bragg reflector of a second conductive type formed on theactive region; a current confinement layer that confines current flowingin the active region; an optical confinement layer that confines lightgenerated in the active region; and an optical loss unit that isprovided in addition to the current confinement layer and the opticalconfinement layer, includes a center portion and a periphery portion ina predetermined direction, and gives a larger optical loss to theperiphery portion than an optical loss given to the center portion.Also, Do1<Do2 and Dn<Do2 are satisfied, where Do1 is a width of anoptical confinement region of the optical confinement layer in thepredetermined direction, Do2 is a width of a current confinement regionof the current confinement layer in the predetermined direction, and Dnis a width of the center portion of the optical loss unit in thepredetermined direction.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described indetail based on the following figures, wherein:

FIG. 1 involves a schematic plan view of a surface emittingsemiconductor laser according to a first exemplary embodiment of thepresent invention, and its cross section;

FIG. 2 involves a schematic plan view of a surface emittingsemiconductor laser according to a second exemplary embodiment of thepresent invention, and its cross section;

FIGS. 3A to 3H illustrate examples of a reflectivity modulationstructure applicable to the surface emitting semiconductor laseraccording to the exemplary embodiments of the present invention;

FIG. 4A is a schematic cross section of a surface emitting semiconductorlaser according to a third exemplary embodiment of the presentinvention, and FIG. 4B is a schematic cross section of a surfaceemitting semiconductor laser according to a fourth exemplary embodimentof the present invention;

FIG. 5A is a schematic cross section of a surface emitting semiconductorlaser according to a fifth exemplary embodiment of the presentinvention, and FIG. 5B is a schematic cross section of a surfaceemitting semiconductor laser according to a sixth exemplary embodimentof the present invention;

FIG. 6 is a schematic cross section of a surface emitting semiconductorlaser according to a seventh exemplary embodiment of the presentinvention;

FIG. 7 is a schematic cross section of a surface emitting semiconductorlaser according to an eighth exemplary embodiment of the presentinvention;

FIG. 8 is a schematic cross section of a surface emitting semiconductorlaser according to a ninth exemplary embodiment of the presentinvention;

FIG. 9 is a schematic cross section of a surface emitting semiconductorlaser according to a tenth exemplary embodiment of the presentinvention;

FIG. 10 involves a schematic plan view of a surface emittingsemiconductor laser according to an eleventh exemplary embodiment of thepresent invention, and its cross sections;

FIG. 11 involves a schematic plan view of a surface emittingsemiconductor laser according to a twelfth exemplary embodiment of thepresent invention, and its cross sections;

FIG. 12 involves a schematic plan view of a surface emittingsemiconductor laser according to a thirteenth exemplary embodiment ofthe present invention, and its cross sections;

FIG. 13 is a schematic cross section of a surface emitting semiconductorlaser according to a fourteenth exemplary embodiment of the presentinvention;

FIGS. 14A and 14B are illustrations explaining oscillation in a highermode of a surface emitting semiconductor laser having a two-layerselective oxidation structure without a reflectivity adjustment member;

FIGS. 15A to 15C are schematic cross sections of manufacturing steps ofthe surface emitting semiconductor laser according to the thirteenthexemplary embodiment of the present invention; FIGS. 16D to 16F areschematic cross sections of manufacturing steps of the surface emittingsemiconductor laser according to the thirteenth exemplary embodiment ofthe present invention;

FIGS. 17G to 17I are schematic cross sections of manufacturing steps ofthe surface emitting semiconductor laser according to the thirteenthexemplary embodiment of the present invention;

FIGS. 18J to 18L are schematic cross sections of manufacturing steps ofthe surface emitting semiconductor laser according to the thirteenthexemplary embodiment of the present invention;

FIGS. 19A and 19B are schematic cross sections showing configurations ofsurface emitting semiconductor laser devices, in each surface emittingsemiconductor laser device, an optical member being mounted on thesurface emitting semiconductor laser according to any of the exemplaryembodiments;

FIG. 20 illustrates a configuration example of a light source deviceusing the surface emitting semiconductor laser according to any of theexemplary embodiments; and

FIG. 21 is a schematic cross section showing a configuration of anoptical transmitter using the surface emitting semiconductor laserdevice shown in FIG. 19A.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention are described below withreference to the drawings. In the following description, a surfaceemitting semiconductor laser (vertical cavity surface emitting laser,VCSEL) is described as an example, and the surface emittingsemiconductor laser is called VCSEL. The scales of the drawings areincreased for easier understanding of features of the exemplaryembodiments, and it is to be noted that the scales are not necessarilyequivalent to the scales of an actual device.

Embodiments

FIG. 1 involves a schematic plan view of a selective oxidation VCSEL 10according to a first exemplary embodiment of the present invention, andits cross section. As shown in the drawing, the VCSEL 10 according tothis exemplary embodiment includes an n-type lower distributed braggreflector, hereinafter, referred to as DBR) 102 formed on an n-type GaAssubstrate 100 and having alternately stacked AlGaAs layers withdifferent Al compositions as a high refractive index layer and a lowrefractive index layer, an active region 104 formed on the lower DBR 102and having a quantum well layer arranged between upper and lower spacerlayers, and a p-type upper DBR 106 formed on the active region 104 andhaving alternately stacked AlGaAs layers with different Al compositions.

The n-type lower DBR 102 is, for example, a multilayer stack including apair of an Al_(0.9)Ga_(0.1)As layer and an Al_(0.3)Ga_(0.7)As layer.Each layer has a thickness of λ/4 n_(r) (where λ is an oscillationwavelength, and n_(r) is a refractive index of a medium). These layersare alternately stacked with 40 periods. The carrier density of thelower DBR 102 doped with silicon, which is an n-type impurity, is, forexample, 3×10¹⁸ cm⁻³. The lower spacer layer of the active region 104is, for example, an undoped Al_(0.6)Ga_(0.4)As layer, the quantum wellactive layer is an undoped Al_(0.11)Ga_(0.89)As quantum well layer andan undoped Al_(0.3)Ga_(0.7)As barrier layer, and the upper spacer layeris an undoped Al_(0.6)Ga_(0.4)As layer. The p-type upper DBR 106 is, forexample, a multilayer stack including a pair of an Al_(0.9)Ga_(0.1)Aslayer and an Al_(0.3)Ga_(0.7)As layer. Each layer has a thickness of λ/4n_(r). These layers are alternately stacked with 24 periods. The carrierdensity of the upper DBR 106 doped with carbon, which is a p-typeimpurity, is, for example, 3×10¹⁸ cm⁻³.

A first oxidation confinement layer 110 is formed at the uppermost layerof the lower DBR 102 or at a position close to the active region 104.The first oxidation confinement layer 110 includes an oxidation region110A that is selectively oxidized and a conductive non-oxidation region110B surrounded by the oxidation region 110A. The first oxidationconfinement layer 110 is desirably formed of an n-type AlAs; however,the first oxidation confinement layer 110 may be formed of an AlGaAswith an Al composition increased to attain, for example, about 99%. Thefirst oxidation confinement layer 110 confines light generated in theactive region 104 within the non-oxidation region 110B with a higherrefractive index than that of the oxidation region 110A and causesoscillation in a fundamental transverse mode. Of course, the firstoxidation confinement layer 110 may also increase the density ofelectrons implanted to the active region 104.

A contact layer 106A is formed at the uppermost layer of the upper DBR106. The contact layer 106A is formed of a GaAs with a high density of ap-type impurity. Also, a second oxidation confinement layer 120 isformed at the lowermost layer of the upper DBR 106 or at a positionclose to the active region 104. The second oxidation confinement layer120 is formed of a p-type AlAs. The second oxidation confinement layer120 includes an oxidation region 120A that is selectively oxidized and aconductive non-oxidation region 120B surrounded by the oxidation region120A. The second oxidation confinement layer 120 is desirably formed ofa p-type AlAs; however, the second oxidation confinement layer 120 maybe formed of an AlGaAs with an Al composition increased to attain, forexample, about 99%. The second oxidation confinement layer 120 confinescarriers (positive holes) so that the implantation density of thecarriers implanted to the active region 104 is increased. Of course,since the non-oxidation region 120B of the second oxidation confinementlayer 120 has a higher refractive index than that of the oxidationregion 120A, the non-oxidation region 120B may have an opticalconfinement function.

By etching semiconductor layers from the upper DBR 106 to the lower DBR102, a cylindrical mesa (a columnar or substantially columnar structure)M is formed on the substrate 100. Etching for the mesa M may beperformed by a depth that allows at lease the first oxidationconfinement layer 110 to be exposed from a side surface. The first andsecond oxidation confinement layers 110 and 120 are exposed from theside surface of the mesa M, and hence the oxidation regions 110A and120A that are selectively oxidized from the side surface are formed. Inan oxidation step, the oxidation rate of an AlAs layer is higher thanthe oxidation rate of an AlGaAs layer, and the oxidation progresses at asubstantially constant speed from the side surface of the mesa M to theinside. Hence, the planar shapes of the non-oxidation regions 110B and120B in planes parallel to the principal plane of the substrate 100 arecircular shapes that reflect the outside shape of the mesa M, and thecenters are aligned with the center of the axial direction of the mesaM, i.e., the optical axis.

In this exemplary embodiment, as shown in FIG. 1, a diameter Do1 of thenon-oxidation region 110B of the first oxidation confinement layer 110is smaller than a diameter Do2 of the non-oxidation region 120B of thesecond oxidation confinement layer 120. The first oxidation confinementlayer 110 confines light so that light in a fundamental transverse modeis generated. The diameter Do1 is, for example, about 3 μm in awavelength range of 780 nm. The second oxidation confinement layer 120confines current that is implanted to the active region 104. Thediameter Do2 is, for example, 7 μm. The first and second oxidationconfinement layers 110 and 120 are desirably simultaneously oxidized;however, the oxidation rates depend on the film thicknesses or the Alcompositions. For example, the larger the film thickness of an AlAs, thehigher the oxidation rate. Hence, the film thickness of the firstoxidation confinement layer 110 is formed to be larger than the filmthickness of the second oxidation confinement layer 120. It is to benoted that the first oxidation confinement layer 110 desirably has afilm thickness that does not noticeably affect the reflectivity of thelower DBR 102 and the reflectivity of the upper DBR 106. For example,the first oxidation confinement layer 110 is an AlAs with a filmthickness of about 30 μm, and the second oxidation confinement layer 120is an AlAs with a film thickness of about 20 μm. Alternatively, the Alcomposition of the first oxidation confinement layer 110 may beincreased as compared with the Al composition of the second oxidationconfinement layer 120, so that a difference is generated between theoxidation rates of the first and second oxidation confinement layers 110and 120.

As described above, since the first oxidation confinement layer 110confines light and the second oxidation confinement layer 120 confinescurrent, the non-oxidation region 120B of the second oxidationconfinement layer 120 may have a relatively large area. Also, thediameter Do1 of the first oxidation confinement layer 110 may beoptimized. Accordingly, the resistance of an element is decreased andthe output of the element is increased.

Also, an interlayer insulating film 130 is formed to surround thebottom, side, and the peripheral edge of the top of the mesa M. Theinterlayer insulating film 130 is formed of, for example, siliconnitride (SiN). A ring-shaped or substantially ring-shaped p-sideelectrode 140 made of metal is formed at the top of the mesa M exposedfrom the interlayer insulating film 130. The p-side electrode 140 isformed of metal by stacking, for example, Au or Ti/Au. The p-sideelectrode 140 is connected with the contact layer 106A of the upper DBR106 by ohmic contact. A circular opening that defines a light emittingopening is formed at the center of the p-side electrode 140. The centerof the light emitting opening is desirably aligned with the optical axisof the mesa M. In other words, the center of the light emitting openingis substantially aligned with the centers of the non-oxidation regions110B and 120B. An n-side electrode 142 is formed at the back surface ofthe substrate 100. The n-side electrode 142 is electrically connectedwith the lower DBR 102.

A reflectivity adjustment member 150 is formed at the top of the mesa Mto cover the light emitting opening of the p-side electrode 140. Thereflectivity adjustment member 150 is made of a material that transmitslight with an oscillation wavelength. The reflectivity adjustment member150 causes an optical loss of a periphery portion to be larger than thatof a center portion 152 near the optical axis of the light emittingopening. The reflectivity adjustment member 150 desirably has a functionof decreasing the reflectivity of the periphery portion as compared withthe reflectivity of the center portion 152. Although described later,the center portion 152 is a region with a smaller film thickness thanthat of the periphery portion, and is defined by a diameter Dn. Thereflectivity adjustment member 150 restricts oscillation in a high-orderhigher mode by decreasing the reflectivity of the periphery portion ofthe upper DBR 106.

The reflectivity adjustment member 150 uses, as a material thattransmits light with the oscillation wavelength, SiN, SiON, or SiO₂. Therefractive index and film thickness of the reflectivity adjustmentmember 150 are selected so that the reflectivity of the center portionof the upper DBR 106 near the optical axis becomes high and thereflectivity of the periphery portion becomes low. The film thickness ofthe center portion is desirably λ×x/2n₁, and the film thickness of theperiphery portion is desirably λ×(y+½)/2n₁. Herein λ is an oscillationwavelength, x and y are natural numbers (including 0), and n₁ is arefractive index of the reflectivity adjustment material. For example,the reflectivity of the center portion of the upper DBR 106 is 99.5%,the reflectivity of the periphery portion is 98.0%, and the differencein reflectivity is 1.5%. If the reflectivity of the upper DBR 106becomes 99% or lower, laser oscillation becomes difficult.

When the mesa M is cylindrical, the light emitting opening of the p-sideelectrode 140 is also desirably formed in a circular shape. The centerportion of the reflectivity adjustment member 150 is also formed in acircular shape correspondingly. The diameter Dn of the center portion152 of the reflectivity adjustment member 150 is between the diametersDo1 and Do2 of the non-oxidation regions 110B and 120B of the first andsecond oxidation confinement layers 110 and 120. Hence, Do1<Dn, Dn<Do2are established.

Alternatively, relationships of Do1<Do2 and Dn<Do2 are established. Forexample, when Do1 is 5 μm, Dn=6 to 8 μm, and Do2>9 μm. When Do1 is 3 μm,Dn=4 to 6 μm, and Do2>7 μm. The optimal value of the diameter Do1 variesdepending on the film thickness, structure, and position in DBR of theoxidation confinement layer, as well as the oscillation wavelength.Therefore, the optimal value of the diameter Do1 is not always uniquelydetermined. Also, the above-described relationship may be Do1 Dn<Do2.

With the VCSEL 10 according to this exemplary embodiment, oscillation ina high-order higher mode, which may be generated at a position in aradial direction corresponding to a larger diameter than the diameterDo1 of the non-oxidation region 110B, is restricted at the peripheryportion of the reflectivity adjustment member 150. In contrast,oscillation in a fundamental transverse mode for light confined withinthe non-oxidation region 110B is promoted at the center portion of thereflectivity adjustment member 150.

FIGS. 14A and 14B illustrate an example of a VCSEL having a two-layeroxidation structure without a reflectivity adjustment member. The VCSELincludes the first and second oxidation confinement layers 110 and 120,the diameter Do1 of the non-oxidation region 110B of the first oxidationconfinement layer 110 has a size for causing oscillation in a singletransverse mode, and the diameter Do2 of the non-oxidation region 120Bof the second oxidation confinement layer 120 is larger than thediameter Do1 (Do1<Do2). However, the VCSEL does not include thereflectivity adjustment member 150 unlike this exemplary embodiment. Insuch a VCSEL, as shown in FIG. 14B, it is found that oscillationconditions are satisfied if the reflectivity of a vertical oscillator is99% or higher and carriers are present at a position near the outer edgecorresponding to a larger diameter than the diameter Do1 of thenon-oxidation region 110B, and high-order higher mode oscillation Lfwhich is not affected by the diameter Do1 of the non-oxidation region110B is generated with priority. That is, a low-order higher mode of afundamental transverse mode is effectively restricted by the diameterDo1 of the non-oxidation region 110B; however, the high-order highermode satisfies the oscillation conditions and oscillation is generated.FIG. 14A schematically shows a near field pattern when viewed from theupper side. In contrast, in the VCSEL 10 according to this exemplaryembodiment shown in FIG. 1, since the reflectivity of the peripheryportion of the reflectivity adjustment member 150 is 99% or lower, theoscillation conditions are not satisfied. As the result, the higher modeoscillation Lf is restricted near the outer edge of the diameter Do1 ofthe non-oxidation region 101B. Also, the oscillation in the fundamentaltransverse mode of light confined by the diameter Do1 of thenon-oxidation region 101B is promoted due to the high reflectivity ofthe center portion 152 of the reflectivity adjustment member 150.

Also, with a VCSEL not having a two-layer oxidation structure but havinga reflectivity modulation structure in which the reflectivity of thecenter portion is higher than the reflectivity of the periphery portionand hence the oscillation in the single transverse mode is available,the difference in reflectivity is not increased. Oscillation in alow-order higher mode (a higher mode next to the fundamental mode) isgenerated with a high current value. This is not suitable for theincrease in output. Further, a step is present in the region where thefundamental mode is present. Hence, a loss is generated due to variationin process etc., resulting in that the current becomes current with ahigh threshold, and variation in optical output appears. In contrast,with the VCSEL according to this exemplary embodiment, the oscillationin the low-order higher mode of the fundamental transverse mode isrestricted by the oxidation confinement layer which is one of thetwo-layer oxidation structure. Also, current is confined by therelatively large oxidation diameter of the other oxidation confinementlayer, and hence the current becomes current with a low threshold.Further, the step by the reflectivity adjustment member restricts theoscillation in the high-order higher mode separated from the fundamentaltransverse mode. A large loss is prevented from being given to thefundamental transverse mode.

In the above-described exemplary embodiment, the mesa M is formed in thecylindrical shape, and the non-oxidation regions 110B and 120B, thelight emitting opening of the p-side electrode 140, and the centerportion 152 of the reflectivity adjustment member 150 are formed in thecircular shapes. However, these shapes are mere examples, and may beother shapes. For example, if the center portion 152 of the reflectivityadjustment member 150 has an elliptic shape, the width of part of theelliptic shape in the longitudinal direction may be larger than thewidth Do2 of the non-oxidation region 120B. As long as the width of thecenter portion 152 of the elliptic shape in a predetermined direction issmaller than the width Do2 of the non-oxidation region, the ellipticshape may pertain to the technical scope of the exemplary embodiment ofthe present invention. Similarly, if the non-oxidation region 110B has ashape other than the circular shape, for example, an elliptic shape, thewidth of part of the non-oxidation region 110B in the longitudinaldirection may be larger than the width of the center portion 152 of thereflectivity adjustment member 150. As long as the width of thenon-oxidation region 110B in the predetermined direction is smaller thanthe width of the center portion 152, the elliptic shape may pertain tothe technical scope of the exemplary embodiment of the presentinvention. Further, if the mesa M performs polarization control byhaving anisotropy in X and Y directions, the mesa M may be formed in anelliptic shape, and the non-oxidation regions 110B and 120B of the firstand second oxidation confinement layers 110 and 120 may have ellipticshapes. Also, the light emitting opening of the p-side electrode 140 mayhave an elliptic shape or other anisotropic shape so that anisotropy isgenerated in the X and Y directions.

Therefore, according to the exemplary embodiment of the presentinvention, only required is that the width Dn in the predetermineddirection of the center portion of the reflectivity adjustment member150, the width Do1 in the predetermined direction of the non-oxidationregion 110B of the confinement layer for confining light, and the widthDo2 in the predetermined direction of the non-oxidation region 120B ofthe confinement layer for confining current satisfy the relationships ofDo1<Do2 and Dn<Do2, or the relationship of Do1≦Dn<Do2.

FIG. 2 involves a schematic plan view of a VCSEL 10A according to asecond exemplary embodiment of the present invention, and its crosssection. In the drawing, the same reference signs are applied to thesame components as those of the first exemplary embodiment. In areflectivity adjustment member 150A according to the second exemplaryembodiment, the reflectivity of a center portion 152A at the lightemitting opening is high and the reflectivity of a periphery portion islow. Unlike the first exemplary embodiment, in the reflectivityadjustment member 150A, the film thickness of the center portion 152A islarger than the film thickness of the periphery portion.

The reflectivity adjustment member 150A desirably uses a dielectric filmof SiN, SiON, SiO₂, or the like, as a material transmitting light withthe oscillation wavelength. The film thickness of the reflectivityadjustment member 150A is λ×x/2n₁, and the film thickness of theperiphery portion is λ×(y+½)/2n₁. Herein λ is an oscillation wavelength,x and y are natural numbers (including 0), and n₁ is a refractive indexof the reflectivity adjustment material. When the refractive index andfilm thickness of the reflectivity adjustment member 150A areappropriately adjusted, for example, the reflectivity of the centerportion of the upper DBR 106 is 99.6%, the reflectivity of the peripheryportion is 98.7%, and the difference in reflectivity is 0.9%.

Next, other configuration examples of the reflectivity adjustment memberaccording to any of the exemplary embodiments are described withreference to FIGS. 3A to 3H. In any of the first and second exemplaryembodiments, the reflectivity adjustment member 150, 150A is formed bychanging the film thickness of the single material. However, thereflectivity adjustment member may be formed of plural materials.Reflectivity adjustment members 150 in FIGS. 3A and 3B are modificationsof the first exemplary embodiment, in which the film thickness of thecenter portion is smaller than the film thickness of the peripheryportion.

In FIG. 3A, the reflectivity adjustment member 150 includes a firstreflectivity adjustment material 160 and a second reflectivityadjustment material 162. The first reflectivity adjustment material 160covers the entire plane of the circular light emitting opening of thep-side electrode 140, and the ring-shaped second reflectivity adjustmentmaterial 162 is stacked so that the center portion of the reflectivityadjustment material 160 is exposed. The region exposed from the secondreflectivity adjustment material 162 defines the center portion 152. Byappropriately selecting the materials and film thicknesses of the firstreflectivity adjustment material 160 and the second reflectivityadjustment material 162, the reflectivity of the center portion isincreased, and the reflectivity of the periphery portion is decreased.In this case, the reflectivity of the periphery portion is desirably 99%or lower. The first reflectivity adjustment material 160 desirably has asmaller refractive index than the refractive index of the semiconductorlayer of the upper DBR 106, and has a film thickness that is odd-numbertimes ½ of the oscillation wavelength. For example, a material of SiON,SiO₂, SiN, or TiO₂ is used. The second reflectivity adjustment material162 has a larger refractive index than the refractive index of the firstreflectivity adjustment material 160, and has a film thickness that isodd-number times ¼ of the oscillation wavelength. For example, amaterial of SiON, SiO₂, SiN, or TiO₂ is used. When the firstreflectivity adjustment material 160 is SiON (refractive index=1.57)with a film thickness of λ/2 and the second reflectivity adjustmentmaterial 162 is SiN (refractive index=1.92) with a film thickness ofλ/4, the reflectivity of the center portion of the upper DBR is 99.7%,the reflectivity of the periphery portion is 98.8%, and the differencein reflectivity is 0.9%.

In FIG. 3B, a first reflectivity adjustment material 160 defined by thediameter Dn is formed on the light emitting opening, and a ring-shapedsecond reflectivity adjustment material 162 is formed around the firstreflectivity adjustment material 160. Even in this case, byappropriately selecting the refractive index and film thickness of thefirst reflectivity adjustment material 160 and the refractive index andfilm thickness of the second reflectivity adjustment material 162, thereflectivity of the center portion becomes higher than the reflectivityof the periphery portion.

FIGS. 3C and 3D are modifications of the second exemplary embodiment, inwhich the film thickness of the center portion is larger than the filmthickness of the periphery portion. In FIG. 3C, a reflectivityadjustment member 150 is formed of a first reflectivity adjustmentmaterial 160 and a second reflectivity adjustment material 162, thefirst reflectivity adjustment material 160 is formed to cover thecircular light emitting opening of the p-side electrode 140, and thecircular second reflectivity adjustment material 162 defined by thediameter Dn is formed on the first reflectivity adjustment material 160.The first reflectivity adjustment material 160 and the secondreflectivity adjustment material 162 desirably have film thickness thatare odd-number times λ/4 of the oscillation wavelength. The refractiveindex of the second reflectivity adjustment material is higher than therefractive index of the first reflectivity adjustment material, and therefractive index of a contact layer of the upper DBR 106 is higher thanthe refractive index of the second reflectivity adjustment material. Forexample, when the first reflectivity adjustment material 160 is SiONwith a film thickness of λ/4 and the second reflectivity adjustmentmaterial 162 is SiN with a film thickness of λ/4, the reflectivity ofthe center portion of the upper DBR is 99.7%, the reflectivity of theperiphery portion is 99.2%, and the difference in reflectivity is 0.5%.

In FIG. 3D, a first reflectivity adjustment material 160 defined by thediameter Dn is formed on the light emitting opening, and a ring-shapedsecond reflectivity adjustment material 162 is formed around the firstreflectivity adjustment material 160. Even in this case, byappropriately selecting the refractive index and film thickness of thefirst reflectivity adjustment material 160 and the refractive index andfilm thickness of the second reflectivity adjustment material 162, thereflectivity of the center portion becomes higher than the reflectivityof the periphery portion.

FIGS. 3E to 3H show examples when a reflectivity adjustment member 150has a three-layer structure. In FIG. 3E, a third reflectivity adjustmentmaterial 164 is stacked on the configuration in FIG. 3A. In FIG. 3F, thethird reflectivity adjustment material 164 is stacked on theconfiguration in FIG. 3B. In FIG. 3G, the third reflectivity adjustmentmaterial 164 is stacked on the configuration in FIG. 3C. In FIG. 3H, thethird reflectivity adjustment material 164 is stacked on theconfiguration in FIG. 3D. The third reflectivity adjustment material 164is formed of a material transmissive for light with the oscillationwavelength. The third reflectivity adjustment material 164 may be thesame as the first and second reflectivity adjustment material 160 and162, or may be different from these materials. By appropriatelyselecting the refractive index and film thickness of the thirdreflectivity adjustment material 164, the reflectivity of the centerportion may be higher than the reflectivity of the periphery portion.

FIG. 4A illustrates a VCSEL 10B according to a third exemplaryembodiment of the present invention. In the VCSEL 10B according to thethird exemplary embodiment, a reflectivity adjustment member 150B isformed of a ring-shaped dielectric film with the inner diameter Dn. Therefractive index and film thickness of the reflectivity adjustmentmember 150B are selected so that the reflectivity of the peripheryportion covered with the reflectivity adjustment member 150B is lowerthan the reflectivity of the exposed center portion.

FIG. 4B illustrates a VCSEL 10C according to a fourth exemplaryembodiment of the present invention. In the VCSEL 10C according to thefourth exemplary embodiment, a reflectivity adjustment member 150C isformed of a circular dielectric film with the diameter Dn. Therefractive index and film thickness of the reflectivity adjustmentmember 150C are selected so that the reflectivity of the center portioncovered with the reflectivity adjustment member 150C is higher than thereflectivity of the periphery portion exposed from the reflectivityadjustment member 150C.

FIG. 5A illustrates a VCSEL 10D according to a fifth exemplaryembodiment of the present invention. In the VCSEL 10D according to thefifth exemplary embodiment, a reflectivity adjustment member 150D has agroove formed at the center portion of the semiconductor layer of themesa M. A circular groove with the diameter Dn is desirably formed byetching the center portion of the contact layer 106A, and the filmthickness of the contact layer 106A is selected so that the reflectivityof the center portion with the contact layer 106A removed is higher thanthe reflectivity of the periphery portion with the contact layer 106Aremaining.

FIG. 5B illustrates a VCSEL 10E according to a sixth exemplaryembodiment of the present invention. In the VCSEL 10E according to thesixth exemplary embodiment, a reflectivity adjustment member 150E has agroove formed at the periphery portion of the semiconductor layer of themesa M. A ring-shaped groove is desirably formed by etching theperiphery portion of the contact layer 106A, and a circular pattern withthe diameter Dn remains at the center portion. The film thickness andthe depth of the groove of the contact layer 106A are selected so thatthe reflectivity of the center portion is higher than the reflectivityof the periphery portion.

FIG. 6 illustrates a VCSEL 1OF according to a seventh exemplaryembodiment of the present invention. In the VCSEL 1OF according to theseventh exemplary embodiment, a reflectivity adjustment member 150F isformed by using a metal material. The p-side electrode 140 is desirablypatterned so that the light emitting opening with the diameter Dn isformed. Accordingly, the reflectivity of the periphery portion coveredwith the p-side electrode 140 is smaller than the reflectivity of thecenter portion with the diameter Dn exposed from the p-side electrode140. In the above-described exemplary embodiment, the reflectivityadjustment member 150F is formed by the p-side electrode 140; however,the reflectivity adjustment member 150F may be formed by using metaldifferent from the p-side electrode.

FIG. 7 illustrates a VCSEL 10G according to an eighth exemplaryembodiment of the present invention. In the VCSEL 10G according to theeighth exemplary embodiment, a high-resistance region 122 is formed byion implanting in the upper DBR 106 instead of the second oxidationconfinement layer 120 provided in the first exemplary embodiment. Byimplanting protons by a constant energy, the ring-shaped high-resistanceregion 122 is desirably formed at a predetermined depth in the upper DBR106. The high-resistance region forms the conductive region with thediameter Do2.

FIG. 8 illustrates a VCSEL 10H according to a ninth exemplary embodimentof the present invention. In the VCSEL 10H according to the ninthexemplary embodiment, a tunnel junction region 124 is formed in theupper DBR 106 instead of the second oxidation confinement layer 120provided in the first exemplary embodiment. The tunnel junction region124 is desirably defined by the diameter Do2 and includes a p-typesemiconductor layer with a high p-type impurity density, and an n-typesemiconductor layer with a high n-type impurity density. When the VCSEL10H is forward biased, the p-type semiconductor layer and the n-typesemiconductor layer are reverse biased, and tunnel current is implantedto the active region 104.

FIG. 9 illustrates a VCSEL 10I according to a tenth exemplary embodimentof the present invention. The VCSEL 10I according to the tenth exemplaryembodiment uses a p-type GaAs substrate, the lower DBR 102 is p-type,and the upper DBR 106 is n-type. The n-side electrode 142 is formed atthe top of the mesa M, and the p-side electrode 140 is formed at theback surface of the substrate. The first oxidation confinement layer 110formed at the lower DBR 102 includes the oxidation region 110A and thenon-oxidation region 110B with the diameter Do2. The second oxidationconfinement layer 120 formed at the upper DBR 106 includes the oxidationregion 110A and the non-oxidation region 120B with the diameter Do1.

FIG. 10 illustrates a VCSEL 10J according to an eleventh exemplaryembodiment of the present invention. The VCSEL 10J according to theeleventh exemplary embodiment differs from the mesa type of the firstexemplary embodiment, and is a hole (trench) type. Plural holes 180, forexample, four holes 180 are desirably formed by etching the upper DBR106 and the lower DBR 102. The plan shape of each hole 180 is a sectorshape with an angle of about 90 degrees. Thin coupling portions 182 areformed between the holes. The first and second oxidation confinementlayers 110 and 120 are oxidized from a side exposed to the holes 180.Similarly to the first exemplary embodiment, the non-oxidation region110B with the diameter Do1 and the non-oxidation region 120B with thediameter Do2 are formed. In this oxidation step, the p-type AlAs andn-type AlAs in the coupling portions 182 are also simultaneouslyoxidized. To restrict leakage of current through the coupling portions182, the resistance of part of the upper DBR 106 and part of the lowerDBR 102 at the coupling portions 182 may be increased by proton ionimplanting. In this case, by adjusting the implantation energy and dosequantity, the resistance of a desirable area of the coupling portions182 (for example, areas indicated by broken lines in the drawing) may beincreased. Even in the eleventh exemplary embodiment, the secondoxidation confinement layer may be replaced with the high-resistanceregion by ion implanting (the eighth exemplary embodiment) or the tunneljunction region (the ninth exemplary embodiment).

FIG. 11 illustrates a VCSEL 10K according to a twelfth exemplaryembodiment of the present invention. The VCSEL 10K according to thetwelfth exemplary embodiment is hole (trench) type. Plural holes 190,for example, four holes 190 are desirably formed by etching the upperDBR 106 and the lower DBR 102. The plan shape of each hole 190 is asector shape. The holes 190 are formed at an interval of about 90degrees, and wide coupling portions 192 are formed between the holes.The first oxidation confinement layer 110 formed at the lower DBR 102 isformed at a position separated from the active region 104. The first andsecond oxidation confinement layers 110 and 120 are oxidized from a sideexposed to the holes 190. Similarly to the first exemplary embodiment,the non-oxidation region 110B with the diameter Do1 and thenon-oxidation region 120B with the diameter Do2 are formed. In theoxidation step, since the coupling portions 192 have relatively largegaps between the holes unlike the eleventh exemplary embodiment, thep-type AlAs and n-type AlAs of the coupling portions 192 are partlyoxidized.

In the twelfth exemplary embodiment, since the first oxidationconfinement layer 110 is formed at the position separated from theactive region 104, a current path P1 passing along the side of theoxidation region 110A is formed in addition to a current path P passingthrough the non-oxidation region 110B. Accordingly, the resistance ofthe element is decreased. The coupling portions 182 have the largewidths and part of the n-type AlAs is oxidized. Hence, the region whichis not oxidized provides the current path P1. Also, to restrict leakageof current in the upper DBR 106 through the coupling portions 192, theresistance of part of the upper DBR 106 at the coupling portions 192 maybe increased by proton ion implanting. In this case, by adjusting theimplantation energy and dose quantity, the resistance of a desirablearea of the coupling portions 192 (for example, areas indicated bybroken lines in the drawing) may be increased. Further, the diameter Do1of the non-oxidation region is increased as compared with a case inwhich the first oxidation confinement layer 110 is arranged close to theactive region 104.

FIG. 12 illustrates a VCSEL 10L according to a thirteenth exemplaryembodiment of the present invention. The VCSEL 10L according to thethirteenth exemplary embodiment is mesa (post)-hole (trench) type. Acylindrical mesa M is desirably formed by a depth to reach at least thesecond oxidation confinement layer 120, and four holes 200 are desirablyformed around the mesa M by a depth to reach at least the firstoxidation confinement layer 110. The holes 200 are formed by etching,and each have a sector plan shape. Wide coupling portions 202 are formedbetween the holes. In the oxidation step, the first oxidationconfinement layer 110 is selectively oxidized from the side surfaceexposed to the holes 200, the second oxidation confinement layer 120 isselectively oxidized from the side surface exposed from the mesa M, andthe non-oxidation regions 110B and 120B with the diameter Do1 and thediameter Do2 are formed.

Even in the thirteenth exemplary embodiment, since the first oxidationconfinement layer 110 is formed at the position separated from theactive region 104, the current path P1 passing along the side of theoxidation region 110A is formed in addition to the current path Ppassing through the non-oxidation region 110B. Accordingly, theresistance of the element is decreased. Also, since the mesa structureis provided, the ions do not have to be implanted to the upper DBR 106unlike the twelfth exemplary embodiment. FIG. 13 illustrates a VCSEL 10Maccording to a fourteenth exemplary embodiment of the present invention.In the VCSEL 10M according to the fourteenth exemplary embodiment, boththe p-side electrode and n-side electrode are formed of surfaceelectrodes. FIG. 13 illustrates an example, in which the VCSEL of mesa(post)-hole (trench) type according to the thirteenth exemplaryembodiment is formed of the surface electrodes. As shown in the drawing,a buffer layer 101 made of an n-type GaAs or AlGaAs is formed on theGaAs substrate 100. In this case, the GaAs substrate may have asemi-insulating characteristic. Similarly to the above-describedexemplary embodiment, the lower DBR 102, the active region 104, and theupper DBR 106 are stacked on the buffer layer 101. The first oxidationconfinement layer 110 is formed in the lower DBR 102, and the secondoxidation confinement layer 120 is formed in the upper DBR 106.

Also, a groove 210 is formed at the side of the bottom of the mesa M.The groove 210 has a depth to reach the buffer layer 101. The interlayerinsulating film 130 is formed on the entire surface of the substrateincluding the mesa M. A contact hole that allows the buffer layer 101 tobe exposed through the groove 210 is formed in the interlayer insulatingfilm 130. The n-side electrode 142 is electrically connected with thebuffer layer 101 through the contact hole. A ring-shaped contact holethat allows the p-side electrode 140 to be exposed is formed in theinterlayer insulating film 130 at the top of the mesa M. An upperelectrode 140A is connected with the p-side electrode 140 through thecontact hole.

A manufacturing method of a VCSEL according to an exemplary embodimentof the present invention is described below. FIGS. 15A to 18L areschematic cross sections of manufacturing steps of the VCSEL accordingto the thirteenth exemplary embodiment of the present invention. Theleft cross section is taken along line B2-B2 with a hole, and the rightcross section is taken along line C2-C2 without a hole.

As shown in FIG. 15A, the lower DBR 102, the active region 104, and theupper DBR 106 are formed on the n-type GaAs substrate 100 bymetal-organic vapor phase epitaxy method (metal-organic chemical vapordeposition, MOCVD). Then, gold is deposited on the upper DBR 106 byliftoff, and hence the ring-shaped or substantially ring-shaped p-sideelectrode 140 is formed.

Then, as shown in FIG. 15B, a SiON film as the first reflectivityadjustment material 160 is deposited. The SiON film is patterned tocover the center portion of the ring-shaped or substantially ring-shapedp-side electrode 140 by a known photolithography step. The SiON filmprotects the light emitting opening and functions as the firstreflectivity adjustment material 160. Then, as shown in FIG. 15C, theSiN film 162 is deposited to cover the entire surfaces of the p-sideelectrode 140 and the SiON film 160. The SiN film 162 functions as anetching mask in later steps, and partly functions as the secondreflectivity adjustment material.

Then, as shown in FIG. 16D, etching is performed on the SiN film 162 sothat an opening H1 that allows the upper DBR 106 to be exposed, aring-shaped opening H2 that allows the p-side electrode 140 to beexposed, and an opening H3 that allows the SiON film 160 to be exposedsimultaneously. The SiON film 160 and the ring-shaped SiN film 162formed thereon form the reflectivity adjustment member 150.

Then, as shown in FIG. 16E, a resist R patterned in a circular shape isformed to cover the openings H2 and H3. The opening H1 is exposed. Then,as shown in FIG. 16F, the resist R and the SiN film 162 present aroundthe outer periphery of the resist R are used as masks, anisotropicetching is performed on the upper DBR 106 through the opening H1, andthe trench (groove) 210 extending to the active region 104 is formed.

Then, as shown in FIG. 17G, the SiN film 162 present at the outerperiphery of the resist R is partly removed by etching, and aring-shaped remaining substance 162A is formed. Then, as shown in FIG.17H, the resist R and the remaining substance 162A are used as masks foretching, and anisotropic etching is performed on the semiconductorlayer. Thus, the cylindrical mesa M is formed on the substrate. Etchinghas to reach at least the second oxidation confinement layer. In theillustrated example, etching reaches the active region 104.Simultaneously with the etching, the hole 200 (see FIG. 12) is formed inthe lower DBR 102 through the trench 210. The hole 200 is defined by adepth to reach the substrate 100.

Then, as shown in FIG. 17I, the resist R is removed, and an oxidationstep is performed. By the oxidation step, the first oxidationconfinement layer 110 is formed in the lower DBR 102, and the secondoxidation confinement layer 120 is formed in the upper DBR 106. When thenon-oxidation region 110B of the first oxidation confinement layer 110has the diameter Do1, the non-oxidation region 120B of the secondoxidation confinement layer 120 is the diameter Do2, and the secondreflectivity adjustment material 162 has the inner diameter Dn, therelationships of Do1<Do2 and Dn<Do2 or the relationship of Do1≦Dn<Do2 issatisfied.

Then, as shown in FIG. 18J, the insulating film 130 is formed to coverthe bottom, side, and top of the mesa M. A contact hole 132 is formed inthe insulating film 130 at the top of the mesa. The contact hole 132allows the p-side electrode 140 to be exposed. Unlike the VCSEL 10Mshown in FIG. 13, the insulating film 130 covers the first reflectivityadjustment material 160 and the second reflectivity adjustment material162 in this exemplary embodiment.

Then, the upper electrode 140A that is connected with the p-sideelectrode 140 is patterned by liftoff or the like. Then, as shown inFIG. 18L, the n-side electrode 142 is formed on the back surface of thesubstrate 100.

In the manufacturing steps D to I of this exemplary embodiment, theprocessing is performed in the same process so that the position of thediameter Dn of the center portion of the reflectivity adjustment memberis aligned with the hole 200 for the trench of the oxidation confinementlayer in the lower DBR 102. Hence, the processing is performed such thatthe center of the diameter Dn is constantly aligned with the center ofthe diameter Do1 of the non-oxidation region. The diameter Dn and thediameter Do are spontaneously aligned. If the center of the diameter Dnis deviated from the center of the diameter Do1, the deviation causes anoptical loss to be generated and oscillation in a single mode isinterrupted. Thus, both the members should be aligned with each other.In contrast, since the diameter Do2 of the first oxidation confinementlayer 120 is larger than the diameter Do1 and the diameter Dn, adeviation is allowable by a certain degree.

Of course, the present invention may be formed of any of theabove-described first to fourteenth exemplary embodiments. Also, thefirst to fourteenth exemplary embodiments may be combined or altered.The VCSEL according to any of the exemplary embodiments of the presentinvention has the wavelength range of 780 nm for example. However, theoscillation wavelength may be desirably determined, and the presentinvention may be applied to oscillation wavelengths from a shortwavelength to a long wavelength. Such a VCSEL is widely used in a lightsource for a laser printer, a light source for optical communication, ora light source for optical sensing. In any of the above-describedexemplary embodiments, the VCSEL of the GaAs type is used for example.However, the present invention may be applied to a VCSEL using othergroup III-V semiconductor. In any of the above-described exemplaryembodiments, the VCSEL of a single spot is used for example. However, amulti-spot VCSEL or a VCSEL array in which multiple mesas(light-emitting portions) are formed on the substrate may be used.

Next, a surface emitting semiconductor laser device, an opticalinformation processor, and an optical transmitter using the VCSELaccording to any of the exemplary embodiments are described withreference to the drawings. FIG. 19A is a cross section showing aconfiguration of a surface emitting semiconductor laser device 300 inwhich the VCSEL and an optical member are mounted (packaged). In thesurface emitting semiconductor laser device 300, a chip 310 having theVCSEL is fixed onto a disk-shaped metal stem 330 through a conductiveadhesive 320. Conductive leads 340 and 342 are inserted into throughholes (not shown) formed in the stem 330. The one lead 340 iselectrically connected with the n-side electrode of the VCSEL and theother lead 342 is electrically connected with the p-side electrode. Arectangular hollow cap 350 is fixed onto the stem 330 containing thechip 310. The cap 350 has an opening 352 at the center. A ball lens 360,which is the optical member, is fixed into the opening 352. The opticalaxis of the ball lens 360 is positioned to be substantially aligned withthe center of the chip 310. When forward driving current is applied tothe leads 340 and 342, laser light is emitted in a vertical directionfrom the chip 310. The distance between the chip 310 and the ball lens360 is adjusted so that the ball lens 360 is arranged within adivergence angle θ of the laser light from the chip 310. Also, alight-receiving element or a temperature sensor for monitoring alight-emitting state of the VCSEL may be included in the cap.

FIG. 19B illustrates a configuration of another surface emittingsemiconductor laser device 302. The surface emitting semiconductor laserdevice 302 includes a flat glass plate 362 fixed at an opening 352 atthe center of the cap 350, instead of using the ball lens 360. Thecenter of the flat glass plate 362 is positioned to be substantiallyaligned with the center of the chip 310. The distance between the chip310 and the flat glass plate 362 is adjusted such that the openingdiameter of the flat glass plate 362 is equal to or larger than thedivergence angle θ of the laser light from the chip 310.

FIG. 20 illustrates an example in which the VCSEL is applied to a lightsource of an optical information processor 370. The optical informationprocessor 370 includes a collimator lens 372 that receives the laserlight from the surface emitting semiconductor laser device 300 or 302with the VCSEL mounted as shown in FIG. 19A or 19B; a polygonal mirror374 that rotates at a constant speed and reflects a bundle of light raysfrom the collimator lens 372 at a constant divergence angle; an f-θ lens376 that receives the laser light from the polygonal mirror 374 andradiates a reflecting mirror 378 with light; the line-shaped reflectingmirror 378; and a photoconductor drum (a recording medium) 380 thatforms a latent image in accordance with reflection light from thereflecting mirror 378. As described above, the VCSEL may be used as alight source in an optical information processor, such as a copier or aprinter, which includes an optical system that collects the laser lightfrom the VCSEL onto the photosensitive drum, and a mechanism that causesthe collected laser light to scan on the photoconductor drum.

FIG. 21 is a cross section showing a configuration of an opticaltransmitter 400 when the surface emitting semiconductor laser deviceshown in FIG. 19A is applied to the optical transmitter. The opticaltransmitter 400 includes a cylindrical housing 410 fixed to the stem330, a sleeve 420 integrally formed at an end surface of the housing410, a ferrule 430 held within an opening 422 of the sleeve 420, and anoptical fiber 440 held by the ferrule 430. An end of the housing 410 isfixed to a flange 332 formed in the circumferential direction of thestem 330. The ferrule 430 is accurately positioned at the opening 422 ofthe sleeve 420. The optical axis of the optical fiber 440 is alignedwith the optical axis of the ball lens 360. The core wire of the opticalfiber 440 is held within a through hole 432 of the ferrule 430. Thelaser light emitted from the surface of the chip 310 is collected by theball lens 360. The collected light incidents on the core wire of theoptical fiber 440 and is transmitted. In the above-described example,the ball lens 360 is used. However, other lens, such as a biconvex lensor a planoconvex lens, may be used. Further, the optical transmitter 400may include a drive circuit that applies an electric signal to the leads340 and 342. Further, the optical transmitter 400 may include areceiving function that receives an optical signal through the opticalfiber 440.

The foregoing description of the exemplary embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in the art. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, therebyenabling others skilled in the art to understand the invention forvarious embodiments and with the various modifications as are suited tothe particular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

What is claimed is:
 1. A surface emitting semiconductor laser,comprising: a substrate; a first semiconductor distributed braggreflector of a first conductive type formed on the substrate; an activeregion formed on the first semiconductor distributed bragg reflector; asecond semiconductor distributed bragg reflector of a second conductivetype formed on the active region; a current confinement layer thatconfines current flowing in the active region; an optical confinementlayer that confines light generated in the active region; and an opticalloss unit that is provided in addition to the current confinement layerand the optical confinement layer, includes a center portion and aperiphery portion in a predetermined direction, and gives a largeroptical loss to the periphery portion than an optical loss given to thecenter portion, wherein Do1<Do2 and Dn<Do2 are satisfied, where Do1 is awidth of an optical confinement region of the optical confinement layerin the predetermined direction, Do2 is a width of a current confinementregion of the current confinement layer in the predetermined direction,and Dn is a width of the center portion of the optical loss unit in thepredetermined direction.
 2. The surface emitting semiconductor laseraccording to claim 1, wherein Do1≦Dn<Do2 is satisfied.
 3. The surfaceemitting semiconductor laser according to claim 1, wherein the opticalloss unit is formed in a light emitting region on the secondsemiconductor distributed bragg reflector.
 4. The surface emittingsemiconductor laser according to claim 1, wherein the currentconfinement layer and the optical confinement layer are formed byselectively oxidizing semiconductor layers.
 5. The surface emittingsemiconductor laser according to claim 1, wherein the currentconfinement layer is formed by implanting an ion to a semiconductorlayer, and wherein the optical confinement layer is formed byselectively oxidizing a semiconductor layer.
 6. The surface emittingsemiconductor laser according to claim 1, wherein the currentconfinement layer includes a tunnel junction region, and wherein theoptical confinement layer is formed by selectively oxidizing asemiconductor layer.
 7. The surface emitting semiconductor laseraccording to claim 1, wherein the optical loss unit decreases areflectivity of the periphery portion by a larger value as compared witha reflectivity of the center portion.
 8. The surface emittingsemiconductor laser according to claim 1, wherein the optical loss unitincludes at least a dielectric film formed on the second semiconductordistributed bragg reflector.
 9. The surface emitting semiconductor laseraccording to claim 1, wherein the optical loss unit is formed by etchingat least a topmost layer of the second semiconductor distributed braggreflector.
 10. The surface emitting semiconductor laser according toclaim 1, wherein the optical loss unit includes a metal film formed onthe second semiconductor distributed bragg reflector.
 11. The surfaceemitting semiconductor laser according to claim 1, wherein asubstantially columnar structure is formed on the substrate, wherein thecurrent confinement layer and the optical confinement layer are formedin the substantially columnar structure, and wherein the optical lossunit is formed at a top of the substantially columnar structure.
 12. Thesurface emitting semiconductor laser according to claim 1, wherein aplurality of holes extending from the second semiconductor distributedbragg reflector to the first semiconductor distributed bragg reflectorare formed, and wherein the current confinement layer and the opticalconfinement layer include an oxidation region that is selectivelyoxidized through the holes.
 13. The surface emitting semiconductor laseraccording to claim 1, wherein a substantially columnar structure isformed on the substrate by removing the second semiconductor distributedbragg reflector, wherein a plurality of holes are formed in the firstsemiconductor distributed bragg reflector exposed from the substantiallycolumnar structure, wherein the current confinement layer includes anoxidation region that is selectively oxidized from a side surfaceexposed from the substantially columnar structure, and wherein theoptical confinement layer includes an oxidation region that isselectively oxidized through the holes.
 14. The surface emittingsemiconductor laser according to claim 1, wherein the opticalconfinement layer is formed in the first semiconductor distributed braggreflector, wherein the current confinement layer is formed in the secondsemiconductor distributed bragg reflector, and wherein a distance fromthe active region to the optical confinement layer is larger than adistance from the active region to the current confinement layer. 15.The surface emitting semiconductor laser according to claim 1, whereinthe width Do1 of the optical confinement layer is a size that causesoscillation in a fundamental transverse mode.
 16. A surface emittingsemiconductor laser device, comprising: the surface emittingsemiconductor laser according to claim 1, and an optical member, lightfrom the surface emitting semiconductor laser being incident on theoptical member.
 17. An optical transmitter, comprising: the surfaceemitting semiconductor laser device according to claim 16, and atransmitting unit that transmits laser light emitted from the surfaceemitting semiconductor laser device through an optical medium.
 18. Aninformation processor, comprising: the surface emitting semiconductorlaser according to claim 1, a light collecting unit that collects laserlight emitted form the surface emitting semiconductor laser on arecording medium, and a mechanism that causes the laser light collectedby the light collecting unit to scan on the recording medium.
 19. Amanufacturing method of a surface emitting semiconductor laser, thesurface emitting semiconductor laser including a substrate, a firstsemiconductor distributed bragg reflector of a first conductive typeformed on the substrate, an active region formed on the firstsemiconductor distributed bragg reflector, and a second semiconductordistributed bragg reflector of a second conductive type formed on theactive region, the method comprising: forming a substantiallyring-shaped electrode having an opening on the second semiconductordistributed bragg reflector; forming a first dielectric film that coversthe opening of the electrode; forming a second dielectric film thatcovers the first dielectric film; forming a first opening that allowsthe second semiconductor distributed bragg reflector to be exposed and asecond opening that allows the first dielectric film to be exposed, inthe second dielectric film by etching the second dielectric film;forming a substantially columnar structure on the substrate by etchingat least the second semiconductor distributed bragg reflector whileusing at least the second dielectric film that defines the first openingas a mask; forming a current confinement layer that confines currentflowing in the active region by selectively oxidizing a semiconductorlayer of the second semiconductor distributed bragg reflector from aside surface of the substantially columnar structure; and forming anoptical confinement layer in the first semiconductor distributed braggreflector, the optical confinement layer confining light generated inthe active region, wherein Do1<Do2 and Dn<Do2 are satisfied, where Do1is a width of an optical confinement region of the optical confinementlayer in a predetermined direction, Do2 is a width of a currentconfinement region of the current confinement layer in the predetermineddirection, and Dn is a width of the second opening of the seconddielectric layer in the predetermined direction, and wherein areflectivity of a region of the first dielectric film covered with thesecond dielectric film is lower than a reflectivity of a region of thefirst dielectric film not covered with the second dielectric film. 20.The manufacturing method according to claim 19, wherein the forming theoptical confinement layer includes forming a plurality of holes in thefirst semiconductor distributed bragg reflector, and forming the opticalconfinement layer that is selectively oxidized in the firstsemiconductor distributed bragg reflector through the plurality ofholes, and wherein the optical confinement layer and the currentconfinement layer are simultaneously formed.